Foams containing compounds that kill roots and/or retard root growth are used to mitigate or prevent blockage of sewer lines by plant roots. Aqueous suspensions, solutions, and mixtures containing the rooticide sodium methyldithiocarbamate (metam-sodium, hereafter referred to as SMDC) are often used to treat sewer lines because such treatment generally does not kill a plant whose roots are eradicated by the SMDC. However, SMDC degrades relatively rapidly at working concentrations in water, a half-life of dilute working concentrations of aqueous SMDC being about 28 minutes. Aqueous stock solutions of SMDC, which are typically about 30% SMDC by weight in water, are relatively stable because the SMDC is not fully solvated by the water.
Because SMDC is a very effective rooticide, aqueous SMDC at working concentrations can maintain effective potency for many hours, and may remain potent for about a day, despite the lability of relatively dilute SMDC in water. A great deal of SMDC is nevertheless wasted because of its degradation in water, and batches of degraded aqueous SMDC are frequently discarded. An alternative to mixing batches of SMDC in water in anticipation of delivering most or all of the entire batch within a few hours is therefore highly desirable.
Sewer cleaning vehicles are typically equipped with beneficial components that are advantageous for delivering foam into sewer lines. The beneficial components include large water tanks, long hoses with jet nozzles adapted to travel into and through sewer lines, and air compressors. However, while the large water tanks are useful for making foam, the aforementioned problem with creating large batches of SMDC at working concentrations creates a serious drawback to using sewer cleaning vehicles for making and delivering rooticidal foam. Moreover, sewer cleaning vehicles can be difficult to modify for making and delivering foam because the vehicles are typically packed tight with sewer cleaning components, leaving little space for adding or rearranging components in order to facilitate foam making and delivery.